JWright, if you’re hypocaloric or isocaloric you may very well gain strength through increased motor unit recruitment and power through decreased time to peak tension without adding one gram of mass. If you’re hypercaloric the same training will probably result in some hypertrophy as the body attempts to increase strength potential through increases in cross-sectional area of the muscles.
It is possible to become denser without necesarrily increasing your displacement volume (size) however your mass would increase. For more info on that check out Ripped Rugged and Dense by our very own Joel Marion.
Growing larger almost always results in growing stronger (even if only slightly) whereas growing stronger may result in absolutely no change in mass (pure neural adaptation).
I hope that clarifies things a little.